Increases in free cytoplasmic calcium (Ca2+) levels as measured by the fluorescent Ca2+ indicator Quin-2, release of inositol phosphates from phosphatidyl inositol and histamine release were examined in histamine-releasing (2H3) and nonreleasing (1A3) clones of rat basophilic leukemia (RBL) cells. In cells passively sensitized with monoclonal IgE, cross-linking of IgE with antigen or concanavalin-A resulted in release of inositol phosphates (PI response), increase in cytosol Ca2+ levels (Ca response) and histamine release in 2H3 cells. None of these responses were observed in 1A3 cells. In 2H3 cells, cytosol Ca2+ reached maximal level (1 MuM) by 2.75 min and then declined over the course of 40 min to levels observed before stimulation (0.11 MuM). Rates of inositol phosphate release were correlated with the actual increase in cytosol Ca2+ level (i.e. Delta[Cai] was observed only when (Cai) had reached maximum levels. All 3 responses were dependent on continued presence of 3 factors; external Ca2+, ligand and cellular ATP production and showed similar concentration-response relationships to varying concentrations of ligand or external Ca2+. Removal or blockade of any of the factors resulted in arrest (within 40 sec.) of all responses. Although histamine release was dependent on increases in cytosol Ca2+, it could be uncoupled from the two other events. Histamine release, but not PI or Ca responses, was suppressed in cells arrested in mitosis with Nocodazole or in cells exposed to 100 MuM Zn2+. PI response could not be uncoupled from the Ca response. Although the above results indicate that both PI and Ca response are intimately associated, the data provide no clear indication of the relationship between the two.